Event - How to unlock
Ice Water - Place 2nd or better in standings in Volcano Void.
Infinity Circuit - Place 1st in standings in Ice Water.
Null Prime - Place 3rd or better in standings in Wet Wasteland.
Primus Dominus - Place 1st in standings in Inifinity Circuit.
Volcano Void - Place 2nd or better in standings in Null Prime.
Wet Wasteland - Place 3rd or better in standings in Beginner's Luck.

Karts
Kart - How to unlock
Plasma Tank - Beat Total Time in Tidal Tundra Time Trial.
Plumber Ship - Beat Total Time in Azmuth Forge Time Trial.
Rust Bucket - Beat Total Time in Necrofriggan Valley Time Trial.
Ship - Beat Total Time in Whirlpool Core Time Trial.
Vreedle Truck - Beat Total Time in Bubble Rabble Time Trial.